1. Field of the Invention
The present invention relates to an automatic document feeder for an image forming apparatus. More particularly, the present invention relates to an automatic document feeder for an image forming apparatus that automatically separates and delivers sheets of paper.
2. Description of the Related Art
An image forming apparatus is generally a device used to form a visual image onto a sheet of paper with regard to an image signal. During the process of forming an image, a developer receives a digital image signal and then causes toner to be attached to an electrostatic latent image made on a photosensitive medium. Accordingly, a toner image is then transferred to a sheet of paper and heated thereon by a fixing roller such that the heated toner image is fixedly melted and thereby forming a visual image.
Such an image forming apparatus, especially a multi-functional device or a scanner, employs an automatic document feeder for automatically separating sheets of an original document to be scanned, and then supplying them to a scan module.
FIG. 1 is a lateral sectional view which shows a configuration of a conventional automatic document feeder for an image forming apparatus. FIGS. 2 and 3 are lateral sectional views for explaining an operation of the conventional automatic document feeder depicted in FIG. 1.
Referring to FIG. 1, an automatic document feeder 10, mounted on an image forming apparatus (not shown), includes an upper cover 11, a scan module 20 installed under the automatic document feeder 10 to scan sheets of paper P, a glass plate 22 over which the sheets of paper are transferred during scanning and which is placed above the scan module 20, and a white bar 21 to guide the sheets of paper P closely along the glass plate 22 during scanning.
The automatic document feeder 10 further includes a document loading tray 12 for storing the sheets of paper P, a pickup roller 13 for drawing the sheets of paper P stacked in the document loading tray 12, and a separation roller 14 for separating the sheets of paper P drawn up by the pickup roller 13 one by one, and moving them in a scanning direction via a friction difference. The automatic document feeder 10 also includes a friction pad 15 installed opposite to the separation roller 14, a pair of feed rollers 16 and 17 installed along the path of the sheets of paper P for moving them to the scan module 20, a discharge roller 18 for unloading sheets of paper P scanned by the scan module 20, and a compression roller 19 installed opposite to the discharge roller 18 for pressing the sheets of paper P against the discharge roller 18 during scanning.
The rollers in the automatic document feeder 10 are actuated by a single driving motor (not shown) and are engaged with one another via a mechanism, such as gears (not shown). When the driving motor rotates, the rollers also rotate. However, if all rollers are designed to rotate simultaneously, the sheets of paper P cannot be separately carried. For this reason, clutches (not shown) are respectively employed so that the corresponding rollers do not rotate when necessary.
Referring to FIG. 2, when the driving motor rotates forward, the pickup roller 13 and the separation roller 14 rotate clockwise to respectively pick up and separate the sheets of paper P. In this case, the clutches prevent the feeding rollers 16 and 17, and the discharge roller 18 from rotating clockwise to prevent scanned and discharged sheets of paper P from being inserted back into the automatic document feeder 10. When a front end of the sheets of paper P reaches the feeding rollers 16 and 17, the driving motor then starts to rotate backward.
Referring to FIG. 3, due to the backward rotation of the driving motor, the feeding roller 16 and the discharge roller 18 rotate counterclockwise to discharge scanned sheets of paper P. While respective clutches make the pickup roller 13 and the separation roller 14 rotate counterclockwise due to the backward rotation of the driving motor, the pickup roller 13 is detached from the sheets of paper P and the separation roller 14 is placed in an idle rotation state due to a feeding force of the sheets of paper.
As described above, since a clutch is employed for each roller to control its rotation direction, the cost of the feeder 10 increases. In addition, since the motion transfer is achieved via gears, the feeder 10 has an increased and complicated volume.
Accordingly, a need exists for an automatic document feeder system having a smaller structure and requiring fewer clutch mechanisms to further reduce paper jams and manufacturing costs.